Wheel dressing mechanism



June 1952 c. w. HOPKINS ET AL 01,290

WHEEL DRESSING MECHANISM Filed March 16, 1945 4 Sheets-Sheet l AG mm AAQ June 24, 1952 c. w. HOPKINS ET AL WHEEL DRESSING MECHANISM 4 Sheets-Sheet 2 Filed March 16, 1945 Z v F June 24, 1952 c. w. HOPKINS ETAL 2,601,290

WHEEL DRESSING MECHANISM Filed March 16, 1945 4 Sheets-Sheet 5 es mg A5 I m/FM 51 CeCH 'W. Hopkins and 5 3051 K. EQ

3a WM June 24, 1952 c. w. HOPKINS EIAL 2,601,290

WHEEL DRESSING MECHANISM Filed March 16, 1945 v I 4 Sheets-Sheet 4 Fig- 8 Elma/whom CecH W. Hopkms and Ro y LEyhar Patented June 24, 1952 UNITED stares rare WHEEL. DRESSING MECHANISM 'Jecil W. Hopkins and Boy I. Eyler, Vi aynesboi'o, Pa 'assignors to Landis Machine "Company, Waynesh'oro, Pa., a corporation'of Pennsylvania Applicationlliarch 16, 1945, Serial No. 583,038

17 Claims.

This invention relates to wheel dressing mechanism, and is "primarily concerned with the provision of a mechanism for accurately contouring the peripheral face of a grinding wheel in counterpart of a predetermined contour to be produced one work-piece in the'operation of said wheel.

In wheel dressing or truing mechanisms heret'ofor'e empmyea for 'thispurpose, diamonds have been used having a cutting ortriturating action upon the "abrasive material of the grinding wheel. l his results 'i'nan appreciable change in wheel diameter, as well as evolving clouds of fine abrasive dust. Despite precautionarymeasures, these minute abrasive particles find their way into the actuating mechanism .for the wheel dressing diamohd so that the accurate functional operation oi the latter is more or less seriously impaired. While such dressing mechanisms may be 'empldyed in case where, in the grinding of certain kinds or work, a high degree of accuracy is not required, they'are not suitable for precision grindin'g, such "as the grinding of a screw thread on work=piecesoi various diameters'where the factors o1"- .pitch, "helix angle and concentricity of thefscrewthre'a'ds are of major importance.

It is, therefore, the general object and purpose o'four present invention to provide a wheel dressin'g'mechanism, in which instead of the usual diamon'd or other cutting tool we employ a hardened steel rdll'er having a surface profile identical with that which is to be produced upon the work, together 'with means for urging said roller under pressure against the peripheral face of the grinding wheel, while said wheel and'roller are relatively rotated, thereby contouring the relatively soft face of the abrasive wheel, so that in the operation of the latter, the desired profile i accurately reproduced upon the work-piece.

It is ano'th'er'object of the invention to provide a mechanism of this kind, particularly designed for use in connection with a centerless grinding machine, and in which weprovide a novel mounting of the wheel dressing or contouring roller, whereby the roller axis may be adjustably inclined relative to the axis of the grinding wheel and substantially in correspondence with the inclination of the work-piece in the grinding throat of the machine.

It is a further object of the invention to provide mean for adjusting the pressure roller to accurat'e'l y compensate for the position of the workpiece in the grinding throat relative to the centers of the grinding and control wheels, which will vary according to the diameter of the workpiece "ando'ther operating conditions.

It is also an additional object of the invention to provide a wheel dressing mechanism of the above character, in which the application and duration of the pressure force of said roller against the face of the abrasive Wheel is independent of the manual force or dexterity of the operator so that the reduction of grinding wheel diameter is held to a minimum and uniformly accurate results are produced.

Our invention further contemplates a dressing mechanism provided with simple and effective means controlling the depth of penetration of the pressure contouring roller into the face of the abrasive "wheel so that when a wheel profile having the predetermined "depth is reached, fur ther penetration of the wheel face by said roller is automatically discontinued.

Yet another object of our invention is to provide certain efiectively operating electrical controls for the wheel dressing roller which are interrelated with the electrical driving system of the grinding wheel and which have for their purpose to reduce the load on the roller operating motor to a ininimum and to also quickly stop the'rota tion of the grinding Wheel so that the wheel dressing operation may be started without excessive loss oi time.

Other subordinate objects of the invention include the provision of a wheel dressing unit hair'- ing a minimum number of structurally durable parts cooperatively assembled in a compact oi"- ganization, in which the several adjusting means for the wheel "dressing roller are easily accessible iorrapi'd operation.

With the above and other objectsin view, the present invention comprises the improved wheel dressing mechanism and operational control system therefor, together with the construction and relativ'e'a'rrangement of the several parts, as will hereinafter he more fully described, illustrated in the accompanying drawings and subsequently incorporated in'the subjoined claims.

In the drawings wherein We have disclosed an illustrative practical embodiment of our invention and in which "similar reference characters designate corresponding parts throughout the several views:

Figure lis aside elevation of the wheeldressing mechanism showing the same mounted in operative position upon a grinding machine;

Figure 2 is a transverse sectional view taken substantially on the line 2-2 of Figure 1, the driving motor for the wheel dressing roller being removed;

Figure 3 is a longitudinal sectional view taken substantially on the line 3-3 of Figure 2;

Figure 4 is a fragmentary horizontal sectional view on an enlarged scale, taken substantially on the line 44 of Figure 3;

Figure 5 is a fragmentary elevation looking at the opposite side of the machine from that shown in Figure l 1 Figure 6 is a transverse sectional view taken substantially on the line 6-6 of Figure 3;

Figure 6a is a detail horizontal section taken substantially on the line (ta-60. of Figure 1.

Figure 7 is a fragmentary sectional view taken substantially on the line l'! of Figure 2;

Figure 8 is a wiring diagram of the electrical control system for the machine, and

Figure 9 is a similar diagram of an alternative method of control.

Referring for the present more particularly to Figures 1, 3 and 6 of the drawings, the wheel dressing unit is rigidly fixed upon a part In of the grinding machine bed above the axis of the grinding wheel I2 and at an angle from the horizonal in close proximity to the grinding wheel for proper operation upon the peripheral face thereof in a manner to be presently described. This angle will vary with the diameter of the grinding Wheel and in some cases the unit may be mounted to operate in a horizontal position.

In the embodiment of the invention which we have selected for purposes of illustration, the dressing unit includes a base [4 extending upwardly and laterally from its fixed end mounted on the bed [(3. On the upper inclined surface of this base the plate It is rigidly secured by means of the screws l8 and is provided intermediate of its ends with a longitudinally elongated opening 2%}. The plate 16 is further provided in its upper surface with a longitudinally extending dove-tailed slideway 22, one side of which has an undercut vertical wall 23 with which a longitudinally slidable tapered key 24 cooperates for the purpose of compensating for wear between the slideway 22 and the mating dove-tail portion on the bottom surface of a slide 26. To each edge of this slide a plate 30 is secured by means of screws 28 and extends downwardly in overlapping relation to the plate I6. These plates exclude abrasive dust and other foreign matter, in all positions of the slide 26, from entrance through the opening 20 and collection upon the parts of the slide operating mechanism to be presently described.

Upon the upper surface of the slide 26, a saddle 32 is transversely adjustable and is keyed against longitudinal movement relative to said slide as shown at 34. This saddle 32 is adapted to be securely held in its adjusted position on the slide by means of the clamping members 36 each of which has a flanged portion for engagement in grooves 38 in the front and rear ends of saddle 32, as clearly seen in Figure 1. These clamping members are secured to the slide 26 by means of the screws 49. When said screws are loosened, the saddle may be trans,- versely adjusted on the slide by means of the adjusting device shown in Figures 2 and 6 of the drawings. With reference thereto, it will be seen that saddle 32 is rovided at one side thereof with a laterally and downwardly extending bracket arm 42. This arm has a tapped hole receiving the adjusting screw 44, the inner end of which has bearing contact with the side plate 38 on slide 26. The bracket arm 42, in spaced relation to the screw 44, is further provided with a counterbored opening in registering relation with an opening in the plate 3i and a tapped hole in the slide 26 which receives the cap screw 46. Thus it will be apparent that transverse movement of the saddle on the slide in one direction is limited by the adjustable screw 44 while movement of said saddle in the opposite direction is limited by contact of the head of the screw 46 with the internal shoulder 47 of the bracket arm 42. Preferably the screw 44 is securely fixed in adjusted position by means ofthe set screw 45. Thus it is possible to easily and quickly make an exact transverse adjustment of the saddle 32 on the slide 26 for the purpose of accurately registering the peripheral surface configuration of the dressing or contouring roller with the preformed peripheral surface of the grinding wheel 52, axially thereof.

The roller cradle 43 is mounted upon the saddle 32 for transverse rocking movement relative thereto, said saddle having an arcuately dove-tailed connection with the cradle 48. The axis of rocking movement of cradle 48 is exactly parallel to the path of movement of the slide 26 which is substantially perpendicular to the axis of grinding wheel l2. The concave slideway in the top surface of the saddle 32 is formed with a rectangular rear side face, as indicated at 5! in Figure 3 of the drawings. Sufficient clearance is provided to permit the cradle 48 to be shifted rearwardly and then vertically lifted to remove the same from connection with the saddle 32. The cradle 48 is retained in any desired angularly adjusted position relative to the saddle 32 by means of the dove-tail clamps 52, shown more particularly in Figures 2 and 7 of the drawings. These clamping members are of cylindrical shape and are retained in suitable recesses formed in the rear side of the saddle 32 by means of the screws 54, each clamp being provided with an undercut inclined shoulder 58 having a curvature substantially identical with the slideway in the saddle 32. The cradle 43 may thus be rigidly held in adjusted position on the saddle by adjusting the screws 54 to force the members 52 inwardly so that shoulders 56 will urge the cradle 48 forwardly and securely clamp its dovetail portion against the forward side wall of the slideway in the saddle 32. The required amount of angular adjustment of the cradle with respect to the saddle is easily measurable by means of suitable indicia 58 engraved upon the forward surface of the cradle 48 in conjunction with the index line 60 on the adjacent surface of saddle 32 (see Figure 6).

In the operation of centerless grinding machines, it is common practice to incline the blade of the work support from the horizontal so that the work-piece will have an endwise movement as it is being ground. In the grinding of roughly pre-formed screw threads on work-pieces this angular inclination of the work-piece should be made equal to the helix angle of the thread. On

the other hand, the thread forming operation is accomplished by means of a grinding Wheel which is formed with a, series of alternating, circumferentially parallel ribs and grooves, and not a continuous thread. In either case, the angle of inclination of the work is variable and the grinding wheel will reproduce its exact peripheral contour on the work, only when that angle with respect to the grinding wheel axis is zero. Consequently it is necessary to axially rock the dressing or contouring roller of our invention relative to the axis of the grinding wheel so that the inclination of the roller axi's willbe equal to that of the work piece from the horizontal in the grinding throat, to produce a slightly skewed or distorted p'rofile upon the periphery'o'f the grinding wheel. Thus, although the grinding wheel rotates -i'n a perpendicular plane normal to its axis, the correct profile will be accurately produced upon the inclined work-piece.

- Upon the upper fiat surface-oi the cradle ts, a bracket 62 is mounted, said bracket having a base portion pivotally connected intermediate of its ends by means of the pin 6 4 with the cradle 43 for pivotal adjustment relative to the latter. Screws are disposed through counter-bored openings'in the rear end of-the cradle fifl andhaving threaded engagement with the bracket 5 2. The "openings are of sufii'ciently greater diameter than the screws 33 topermit lateral movement-oi" said screws in the pivotal adjustment of the bracket "62 which is eff'ec'tedby means of theadjusting screws '7 G threaded in the cradle 48 in perpendicular relation to the screws and respectively-coa'cting therewith. By such pivotal "adjustm-entof 'the'bracket, the dressing or contouring "roller mounted thereon may be easily position'ed with its axis in accurate 'ooincidin'g'rlation with a transverse plane normal to the path of movement of the slide it. Springs i2 surroundingthe screws 56 'are'seated in the enlarged outer'ends 13 of the 'openings'in the cradle "48 and retained therein by the washers it. Similar screws 88 are also disposed through enlarged openings in the bracket "62 and are engaged in tapped openings in the cradle 48. Springs l6 rsurround'ing the screws 88 are seated in the spring cups "58 and retained therein by washers '80. Thus the bracket "62 is resiliently retained in proper position on the cradle '48 when the screws 66 andtB are temporarily loosened for theipivotal adjustment of said "bracket by means of the screws ill.

At "appropriate locations, pads '82 are formed uponthe upper surface of thebracket'SZ "for the installation of an electric driving motor '8 for the wheel dressingroll'er.

"As seen in Figure the "bracket at'its forwardend is formed with "an upwardly projecting part 86 perpendicular to the surface of the cradle 48, and, as shown in Figure 4, is provided in its rant-face witha T-slot '88 in Which the mating rib 91] formed on the roller support 92 is slidably engaged. Screws '95 and Washers 96 areprovided forthe-purpose-of rigidly securing saidsupport in correct vertical position upon the part "86 of the bracket 52. These screws are disposed through vertically elongatedslots '98 in the bracket part 6 6, ancl'the vertical adjustment of the support 92 is'efiected by means of the screw Is!) which is threaded through a rearwardly projecting part I02 on the upper end of the support '92 and has bearing engagement at its lower end upon the upper edge-of the part 86 of bracket fil The vertical adjustment of support S22 is measuredby the position of an index finger or pointer Hill on said support with respect to the indicia I 06 inscribed upon the plate Hi4 attached to bracket 62 (seeFigure 1).

As shown in Figure 4 of the "drawings, the support E2 extends across the front face of bracket part 86 and is provided at one of its ends with :a housing '93 for the ball thrust bearings H O between which similar annular spacers H 2 are positioned. The reduced end of the-dressing roller "shaft IIfi is journalled in these hearings which are retained in position within :the bearing housing es by means of the cap member I16 which is fixed to said housing by means of suitable screws indicated at I13. The extremity of the shaft I It beyond the outer bearing 4 II] i's further reduced in-diameter to receive the sprocket sleeve I20 which is restrained against rotation relation to theshaft bymeans of thekey I22. .A recess in the :end of the sprocket .sleeve I29 receives a flanged clamping 'member I24 which is removably attached to the extremity of the shaft by means 'of the screw I25. In this manner, the inner end of the sprocket sleeve I 20 is firmly heldagainst the outer thrust bearing MB. The sprocket formed on the outer end of said sleeve is operatively connected with a similar sprocket on the drive shaftof motor 8 by means of the chain I23. The sprockets and drive chain are preferably enclosed within a suitable guard housing indicated at I38. Between the annular cap member H3 and the outer surface of the sprocket sleeve I20 a conventional type of grease seal H2 is inserted to effectively retain the lubrieating grease in the bearings II ii while excluding undesirable foreign matter. .A similar seal (I34 is employed at the opposite side of the bearings between shaft IM and the wall of the housing93.

Thesupport $32 at its other end has a slot I35 formed in the front face thereof tore'ceive fairib or key formed upon one side of a bearing housing I38whi'ch is rigidlysecured to the-support 92 by means of screws indicated at I40. This end of the roller shaft N 4 has a threaded section and a terminal portion N5 of reduced diameter extending therefrom upon which the bushing M2 is engaged and keyed against rela tive rotation by means of the pin I i l projecting from the threaded portion of :the shaft I'M into a bore formed in the enlarged inner end of the bushing Hi2. This bushing is journalled in :a bearing I46 mounted in the'housing I38. A nut I48 threaded upon the bushing "and the locking washer I56 retains the bearing in proper axial position. A cap member I 52, removablyvsecured by means of the screws 154 to the housing 438., retains the outer race of the bearing 4'46 in its proper axial position. Agreas'e seal til-tie int-en posed between the cap member I 52 and the bushing M2 and a similar seal --I 58 is provided between the innerend of the bushing and the housing -.I-3'8.

Upon the central portion of the "shaft M4 the hardened steel dressing or contouring roller is fixed against rotation by means of a suitable key I52. The washer I64 and nut I55 engaged upon the threaded portion of the shaft -I.-.I4 securely clamps the roller in a fixed axial rpo'si tion relative to the shaft against the shoulder I68 formed upon said shaft. The peripheralrsurface of the roller IE9 is accurately contoured in accordance with the predetermined contour to be produced on the work. In the present instance, in Figure 4 we have shown this :roller provided with alternating V-shaped ridges and grooves, as at 'IGI, for the purpose of providing the grinding wheel with :a profile contour which will accurately grind screw threads upon a roughly pre-formed work-piece.

On further reference to Figure 3-of the-:dmwing, it will be seen that the slide as is formed with a part 21 depending through the-opening 2c in the plate I6,.said part having two longitudinally spaced apertured lugs I10 and W2 respectively, which are positionedin'a cavity informed in the base I4. lug I'll] is internally threaded to receive an externally threaded :Jbushing I I4 while the aligned aperture of the lug I12 receives a slidable bushing I16 which is internally threaded. The lug I72 is formed with a keyway for the reception of the key I18 carried by the bushing I'I6 so that while said bushing may axially slide relative to the lug I72 it is restrained against rotation with respect thereto. A powerful coil spring I88 is interposed between the bushings I74 and I16 and is supported at its opposite'ends upon reduced diameter portions of the respective bushings. A shaft I82 extends through the bushing I14 in clearance relation thereto and has threaded engagement in the bushing I16 so that the latter bushing acts as a traveling nut to compress the spring I88, as well as to move said bushings, the slide 26 and the various parts supported thereon as a unit relative to the plate I6 and the base I4.

Extending rearwardly from the cavity I5, the base I4 is formed with a longitudinal bore in which the sleeve I84 is non-rotatably mounted for sliding movement by means of a suitable key I86. Through this sleeve an unthreaded section of the shaft I82 extends, the rear end of the sleeve being counter-bored to receive the bearing bushing I98 for said shaft. Rearwardly of this bushing, the end of the shaft I82 is of reduced diameter and has a cylindrical member I92 fixed thereto by means of a key I84. This member is provided with suitably spaced handles I86 pro. jecting rearwardly therefrom by means of which it may be conveniently rotated. A collar I88 is threaded upon the rear extremity of shaft I82 to prevent axial displacement of the member I82 and retain the annular flange 288 thereof in overlapping relation upon the periphery of the diametrically enlarged rear end of the sleeve I84. This flange has a beveled surface with indicia 282 inscribed thereon to cooperate with an index line on the adjacent peripheral surface of the sleeve I84 whereby the rotation of the shaft I62 may be accurately measured.

The sleeve receiving bore through the base I4 is provided at its rear end with the annular shoulder I35 against which the rear end of sleeve I84 is adapted to abut and thereby limit axial forward movement of said sleeve. Axial movement of the sleeve in the forward direction relative to shaft I82 is prevented by contact of the sleeve with the collar I83 formed upon said shaft.

The forward end portion of sleeve I84 is formed with a longitudinal series of external rack teeth 284 which are engaged by the teeth of a pinion 286 secured against rotation relative to the manually operable shaft 288 by the key 2I8. This shaft is transversely mounted in the base I4 and is provided at one end with the handle '2I2 for convenient operation. A lever 2I4 is fixed at one of its ends to the other end of the shaft 288 by the pin indicated at 2I6, and upon rotation of said shaft is adapted to actuate two limit switches 2I8 and 2I9. The properly timed simultaneous operation of these switches is obtained by means of the screws 228 adjustably threaded in the end of the lever 2I4 and locked in adjusted position by means of the nuts 222.

From the above, it will be evident that the mechanism, including shaft I82 and sleeve I84, is rearwardly movable on the base It to the extent permitted by the length of the rack teeth 284. In order to retain the mechanism in this retracted position against the force of gravity, the sleeve I84 is provided with a notch or recess 224 adapted to receive a detent 226 mounted in an opening in the base I4 and constantly urged into contact with the sleeve by the spring 228.

The spring is retained in position and its tension properly adjusted by means of the plug 238 threaded into the outer end of the opening in the base. This spring and the detent, however, offer but negligible resistance to a positive force manually applied to the handle 2I2.

To the top of the roller support 92 one end of a forwardly and downwardly curved bracket member 232 is pivotally connected as at 234. The lower end face of this bracket is recessed to receive a wire brush 236 which is detachably held in proper position by means of the clamping plate 238 and the screws 248. The upper side of the bracket 232 is provided with a recess 242 which contains a compression spring 244 retained therein by means of a cap screw 246 disposed loosely through an opening in the bracket and having threaded engagement in 2. lug or extension projecting from the front face of the support 92. By adjustment of this screw, the pressure of the spring 242 on the bracket 232 may be regulated to yieldingly hold the brush 236 in proper contact with the contoured peripheral surface of the roller I68 so that said brush will operate to continuously remove such particles of abrasive material as may adhere to the contoured surface of the roller I68.

In the operation of centerless grinding machines, it is well understood that due to variation in diameter, metallurgical characteristics and other details, different kinds of work-pieces will occupy a position in the grinding throat at a higher or lower elevation with respect to a common plane intersecting the axes of the grinding and work control Wheels. Therefore, it is usual to provide means for vertically adjusting the work rest blade in the grinding throat. It is apparent that the grinding wheel will not reproduce its contoured profile on the work with equal fidelity or accuracy in all possible positions of the work-piece in the grinding throat. Consequently the peripheral profile 0f the grinding wheel must be altered to compensate for such difference in position of various work-pieces in the grinding throat.

Referring more particularly to Figure 1 of the drawings we accomplish this alteration in the profile of the grinding wheel by adjusting the point of tangential contact between the roller I68 and the grinding wheel to the same relationship with the radius line of the grinding wheel which is parallel to the slide 26, as that which exists between the point of tangential contact of the grinding wheel with the work and a plane intersecting the centers of the grinding wheel and Work control wheel. Thus, as seen in Figure 1, the line of tangency between the roller I68 and the grinding wheel is indicated at A, and, in the position of the roller shown in full lines, the point of tangential contact is substantially coincident with the radius line B intersecting the axes of the grinding wheel and dressing roller I68 and approximately parallel to the slide 26. If the adjusting screw I88 is now operated to adjust the support 92 for a distance measured on the scale I84 to dispose the roller I68 in the dotted line position C, the point of tangential contact of said roller with the periphery of the grinding wheel will then be coincident with the line D, also parallel to slide 26, thus producing aline of thrust of the roller I68 against the grinding wheel spaced from the wheel axis for the 9 that which would be produced with the roller I88 operating in the position shown in full lines in Figure 1.

In preparing the mechanism for operation, the several adjustments above described are first made to position the roller I88 in accordance with the helix angle of the threaded work and the vertical position of the work in the grinding throat. It is also necessary to adjust the position of the roller I80 longitudinally of the base l4 by operation of shaft I82 to move the slide 26 forwardly until exact contact is made between the roller I68 and the periphery of the grinding wheel l2, without removing any abrasive material from the grinding wheel. Thus it is apparent that, when shaft I82 is rotated the threaded section thereof cooperates with nut I18 to move said nut, spring I88, bushing I14 and slide 28 as a unit axially of said shaft. Spring I88 prevents axial movement of nut. I18 relative to the slide 28. This adjustment is made with, the sleeve I84 at the extreme. forward end of its stroke and in contact with stop shoulder I855.

The mechanism is now withdrawn. from the grinding wheel to the extreme, rearward position as limited by the rack teeth 284. Shaft I82 is then rotated by adjustment of the member I82 to move the slide 26 forwardly for an amount measured on scale 282 which is equal to the desired penetration of the peripheral face of the grinding wheel by the roller I88. The handle 212 is. then rotated in a clockwise direction, forcing the sleeve I84, shaftv I82, nut I18, slide 28 and the mechanism supported thereby toward the grinding wheel. Upon contact between. the roller I68; and the face of the, grinding wheel, further forward movement of said roller is resisted and the continued movement. of handle 212 then compresses the spring I88 between the bushing I14 and nut 118, as the latter moves axially with shaft [82. Thus spring {88 is compressed for a distance equal to the pre-set depth of penetration of the. grinding wheel. In this final movement: of the handle 2 l2 to the extreme clockwise position, limit switches 2l8. and 258 are closed and the roller driving motor 84 energized. Thereafter the spring I88 continues to force the slide 26 forwardly and. feed the roller I58 into the face of the grinding wheel; When lug I12 on the slide again. contacts the shoulder I19, on nut I18, further forward movement of the slide and roller I88 ceases and the load on the operating motor 84 for thedressing roller I58 sharply drops. The dressing operation is then completed, and the circuit of motor 82 is automatically opened as will presently be more fully described. The handle 212 is then moved in the counterclockwise direction, returning the roller I68 to its original position relative to the grinding wheel andxthe latter is then prepared. for further operation upon the work-pieces.

If desiredgdiiferent rollers I88 may be employed for grinding screw threads of different helix angles, said rollers having thread profiles which are distorted sufficiently with respect to the threadprofile to be produced on the work to compensate for axial angularity of the work-piece. In this case the adjustable cradle 83 and saddle 32 can be dispensed with and roller supporting bracket 82 mounted directly upon the slide 28.

In Figure 8 of the drawings we have diagrammatically illustrated an electrical control system for the various operating motors duringthe wheel dressing operation. The three phase alternating current line 252 is adapted to be opened or-closed by the main line switch 254. After passing through the fuses 258, the main line is connected with the terminals of the primary coils of transformers 258 and 268. A relay 268 is connected across the secondary coil of transformer 258 by the lines 262 and 284. The separate wires of main line 252 are connected to the contacts 268, 218 and 212 which are normally open and are operated by the relay 266. Thus, when switch 254 is closed, the current, through transformer 258 energizes relay 268, thereby closing the contacts 268, 218 and 212. Contacts 268 and 218 are connected to the heating coil of a thermal overload relay indicated at 214. The contacts of the relay 214 are connected in the line 218 through the secondary coil of transformer 258. Contacts 212 are connected directly to the motor 218 which is also connected to contacts 268 and 218 through the overload relay. Thus, the closing of contacts 258, 218 and 212 will start the motor 218, which is utilized for driving the oil pump 288 in the lubricating system of the grinding machine. Pump 288 is connected hydraulically to the pressure switch 282, so that the starting of. motor 218 results in the closing of switch 282 connected in line 284 which in turn is connected to the other terminal of the secondary coil of transformer258.

The grinding wheel motor 288 is started by depressing the start button 288. This momentarily completes the circuit from point 298 on line 216 through relay 282', contact of thermal overload relay 288', switch 288, stop switch 285, line 286, normally closed contact 288, line 388 to line 284, completing the circuit to transformer 258. Relay 282 is energized, closing contact 382 which creates a holding circuit exclusive of the start button 288, so that current is maintained to relay 282 when said start button is released. Relay 282 when thus energized also. closes the contacts 384, 388 and 888., establishing. a direct circuit from main line 252 through contacts 384, 386 and 388 and the heating coils of thermal overload relay 284 to the grinding wheel motor 288 and starting the motor.

It will be understood that the wheel dressing operation cannot be started until after the grinding wheel has been brought to a complete stop, since otherwise, the abrasive grinding wheel would destroy the peripheral contour of the dressing roller. Therefore when the grinding operation has continued, until it becomes apparent that a dressing or truing operation is necessary, it is desirable that the rotation of the grinding wheel be instantly stopped so that the dressing operation can be initiated without loss of time. Momentum of the heavy grindin wheel and its motor armature tends to continue the rotationof the wheel for a protracted time period, and we have solved this problem by the following control system:

A plugging switch 318' is mechanically connected to the grinding wheel spindle and, during operation of the wheel, maintains the contacts 352 and 8M in lines 316 and 318, respectively, in closed position. Therefore, these contacts remain closed after the stop switch 285 is operated to open the circuit through the grinding wheel motor operating relay 282. The de-energization of the relay 282 allows the normally closed switch contacts 324 to close, establishing a circuit from point 828 on line 216 through relay 322, contacts 324, line 358, switch contact 3|2 and line 325 to line 284. The energization of relay 822 closes contacts 328, 328, 338 and 332. Thus current is conducted from the main line- 252' to contact 325, line? 33.4

1 1 and the alternating current coils of the saturable reactor 336 to 1ine 338 which leads to the grinding wheel motor 286. Current also passes through contacts 328, line 840 and the alternating current coils of saturable reactor 342 to line 344 which leads to the grinding wheel motor 286. The grinding wheel motor 286 is also connected to main line 252 through contacts 338, lines 346, the alternating current coils of saturable reactor 348 and line 350. It will be noted that this connection through contacts 326, 328 and 338 reverses the direction of the current through motor 286 and thus applies an electrical braking force to the armature and wheel spindle which results in a rapid stopping of rotation of the spindle and grinding wheel. Further, the saturable reactors 336, 342 and 348 provide a means for closely regulating the current input to motor 286.

The secondary coil of transformer 260 is connected directly to the alternating current terminals of a bridge rectifier 352. The direct current leaving the rectifier 382 passes through line 354, the direct current coils of saturable reactors 336, 342 and 348, variable resistance 356, contact 360, contact 332 and returns to the rectifier 352 through line 333. It will be noted that the operation of plugging switch 3I0- also energizes relay 364 by means of a circuit from point 366 on line 216 through line 351, relay 364, line 3I8, switch contacts SM and line 325 to line 284, thus closing the normally open contacts 360. By adjus'ting the resistance'356, therefore, the amount of current supplied to motor 286 may be regulated.

The limit switches 2 I 8 and 2I8, above described are contacted by the screws 220 just before the dressing roller I80 touches the grinding wheel and, before contact of roller I 68 with the periphery of the wheel, said. switches are simultaneously closed while spring I80 is being compressed. Since handle 2 I 2 is held in this position until the dressing operation is completed it will be seen that switches 2I8 and 219 remain closed during the dressing operation.

When the switches 2 I 8 and 2 I9 are thus closed, the operating motor 84 for the wheel dressing roller is energized by establishing a circuit from the point 368 on line 216 through line 3153, relay 312, the contacts of thermal overload relay 314, line 316, normally closed contacts 318, limit switch 2I8 and line 380 to line 234. The energization of r relay 312 closes contacts 382, 384, 386, which establishes a direct circuit from line 252 through contacts 382, 384 and 386 and the heating coils of thermal overload relay 314 to the wheel dressing motor 84. It will be observed that the circuit energizing relay 232 for the operation of the grinding wheel motor 288 is held open during the operation of the dresser operating motor 84 since the energization of relay 312 for the latter motor opens the normally closed contacts 288 in the grinding wheel motor circuit. The primary coil of a transformer 368 is installed in the line from contacts 386 to motor 84. Thus, a voltage is induced in the secondary coil of transformer one terminal of which is connected to the filament of a gas filled tube 382 by means of line 384. The other terminal of the secondary coil of transformer .396 is connected through variable resistance 396 and line 398 to the grid of the tube 382.

A transformer primary coil 488 is connected by lines 40I across two wires of the main line 282 and induces a voltage in a secondary winding 45?. connected across the filament of tube 392 by wire 403, and in another secondary winding 484 one terminal of which is connected by wire 485 to the 12 plate of tube 392. The other terminal of winding 484 is connected by line 401 to the relay 406 and through line 488 to the secondary winding'462. A condenser M8 is installed across the terminals of relay 406.

When the motor 84 is started, the voltage induced in the secondary winding of transformer 390 causes tube 382 to function and conduct current from the grid on line 398 to the plate and through winding 404, energizing relay 406. Contact 4I2 then closes and a circuit is established from the point M4 on line 216 through line 4| 6, relay 4I8, contact M2 and line 420 to line 284. This energizes the relay M8 and closes contacts 422 and'424. Thus a holding circuit for relay 312 is established from point 388 on line 216 through 318, 312, 314, 316, 424, 219 and line 426 to line 284.

At the same time, relay 428 is energizedby the following circuit: From point 430 on line 216, through line 432, 428, 422 and line 434 to line 284. Energizing the relay 428 causes the normally closed contact 318 to break the circuit 368, 318, 312, 314, 316, 318, 2I8, 380, 284, but the relay 812 is retained in energized condition by the aforementioned holding circuit. Relay 428 also closes contact 436 providing the following holding circuit for relay 428 after relay 406 is no longer energized; from point 430, 432, 428, 436, 2I8, 380 to 284.

As above described, the de-energization of the grinding wheel motor relay 292' allows the normally closed contacts 324 to close and establish a braking circuit through the plugging switch 3 I 0. This circuit is broken when the grinding wheel finally stops and plugging switch 3I0 opens contacts 3I 2 and 3M. However, when the dresser motor 84 is started, a new circuit is established from point 328 through 322, 324, contacts 438, and line 325 to line 284, thus reapplying the reversing current to the motor of the grinding wheel I2. It is to be noted that, since relay 364 is not energized, the direct current through the saturable'reactors now passes through normally closed contacts 362 and variable resistance 358, which is used to control the current to motor 286 while motor 84 is operating.

By operating the grinding wheel motor 286 while the dressing roller motor 84 is operated the load imposed on the latter motor is appreciably reduced. When the current to motor 286 is adjusted to a value sufficient to overcome the inertia of the motor armature and of the relatively heavy grinding wheel, the load on the roller I and motor 34 is much smaller than would be the case, if it were necessary for the roller I60 to turn the dead weight of the grinding wheel. If desired, this current value supplied to the motor 286 may be such that the grinding wheel is rotated at approximately the same peripheral speed as the dressing roller I66. Thus, as the wheel and roller are rotated in the directions indicated by the arrows in Figure l of the drawings, peripheral friction at the point of tangential contact between said wheel and roller will be absolutely nil so that the formation of the usual cloud of abrasive dust in the immediate vicinity of the machine is substantially absent. However, the pressure force applied by spring I to the roller I60 in the manner above explained results in the penetration of said dressing roller into the relatively soft peripheral face of the grinding wheel to the required predetermined depth with the highly accurate truing or contouring of the wheel profile as may be required to exactly reproduce such profile 13 upon; the work-piece; under predetermined conditions; ofopfiration; as heretofore described.

When. the roller. 1.8.0 has penetrated the, grinding; wheel: It; to. thedesired. depth, further penetration. is mechanically. prevented as above described. When this point is; reached; the motor 84* merely rotates the roller Hill idly and its load current decreases sharply in value to a point insufiicient to operate the tube 392', with the result that relay 4% is ole-energized. This causes the contacts 412 to open and de-energize relay 4l8. Contacts 424 therefore open and de-energize relay 312, opening the line to motor 84 and stopping said motor. Relay428 remains energized through the circuit 30, 432, 428, 436, N8, 388 and 284 and thus prevents the re-establishment of the original circuit to relay 312 by holding contact 318 open. Relay #28 is de-energized when the limit switch 2 I9 is opened and the dressing mechanism is Withdrawn from the wheel 2 to complete-thecycle.

A-nal-ternativemethodof automatical-lystopping the operation of motor he is illustrated in Figure 9. This provides for the installation of the primary winding MB of' a current trans-former in the-motor circuit. A secondary winding" 442 of said transformer is connected to both plates of a full wave rectifier tube M4. Adjustable resistances 446 and 448 are connected from each terminal of the secondary winding M2 toa center tap provided on that winding. The center tan is also connected through line see to relay- 496. Another secondary winding- 652 corresponding to the secondary winding; 402 of Figure 8', is connected to the filament of tube 4% and line 455 connects this circuit to the other terminal of relay 406'. A, protective resistance 456 is installed across lines 450; andfl i'. There is also connected, in parallel: with the secondary Winding 442"; a resistance 458' with the characteristic of offering high resistance at lowvoltage but having a very much reduced resistance value at high voltages. This is merely a protective device for'preventing abnormally high voltages fromdestroying the secondary winding M2.

It. will be evident from the above that the starting current for motor 84 will induce a high volt age across thesecondary 442' ofthe current transformer. This isrectified-by the tube ml l and conducted through relay the, closing contacts 442 and causing the same sequence of events asin the met-hod first described; The variable resistances 3-46 and-'Miipermit pre-setting-of thevoltage value at which relay 485- is de-energized to stop motor 84 when the wheel dressing operation 55 is completed.

From the foregoing description and theaccompanying drawings; it is believed that the several novel features of our invention and the operation thereof may be clearly understood It 60 will be seen that wehave provided a profile dressing or contouring unit for abrasive grind ingwheels which is particularly desirable for use in connection with high precision grinding machinesofthe centerlesstype. In avery com-- pact organization, provision is made formaximum flexibility in the adjustment of'the wheel dressing roller to accurately locate or position its contoured surface with relation to the peripheral surface of the grinding Wheel; so that in the dressing or contouring operation the particular conditions required in the grinding of various different kinds of work-pieces are compensated for and the contoured surface'of thedressing roller will be" reproducedupon the guished. from a. process of attrition, there; will be a minimum. reduction in grinding wheel diam;- eterin each wheel. dressing operation. Also, the automatic, limitationof. the-depth of penetration of the dressing roller into the face, of, the grind- 10 ing wheel obviates, possible inaccuracy due to human failure, andassures that only the exact amount of stock is removed from the WOI'kr-PiGCB in, the grinding operation which is necessary to produce the required contoured surface thereon.

It will, therefore, be appreciated that the i1 1- vention; herein disclosed is particularly desirable for: use in connection with the: grinding of roughly preformed: threads on rods, bolts. or otherwork-pieces of various diameters, where the pitch, helix angle; and concentricity of, the

screw threads are factors of prime importance.

By the, provision of the co-relatedcontrol, circuits for the operating motors of the grinding wheel and the wheel dressing roller, the; rotation 5 of the. grinding wheel may be reversed and the dressing operation quickly inaugurated. It; will further be evident that the several adjustments of the dressing roller above described'to position the same'relative to the axial'center of thegrindli e wheel as well as the advancing and retracting movements of the roller carrying slide 25 can be easily and quickly made. Sincethe accumulation, of abrasive dust upon the several relativeiy movable parts of the mechanism. is un- 5 likely minimum wear of said parts and highly efficient. operation is obtained. It will also be noted that the several cooperating mechanical parts: ar f: r ed durable structura form and may bereadily assembled so that production 40 cost: of:our; improved wheel dressing unit wilLbe reasonably low.

The invention may be embodied in other specificforms without departing from the spirit or essential characteristics thereof; The present 5 embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all' changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein,

What is claimed and; desired to-be secured by United States Letters Patent is:

1. Dressing mechanism for abrasive grinding wheels, comprising a base adapted to be-mounted on amachine frame in proximity to the grinding wheel, a slide movable on said base toward and from the periphery of the wheel, acontoured wheel dressing roller, means mounting said. roller on the slide including means rotatably. supporting. the roller with its axis in a transverse plane normal; to. the path of movement. of the slide, means. operatively associated with the roller supporting means for angularly adjusting the roller supporting means to dispose the roller axis in said planeat a predetermined inclination relative to the axis of the abrasive wheeli, and means mounted in the base andoperatively con- 71) nected with said slide to actuate the latter;- and including springmeans rendered: effective upon COIJtRCSCOfthdIOllGl with thewheel to resiliently urge the contoured surface Of said roller under pressure into the peripheral face. of the. abrasive 76 wheel.

2. The combination defined in claim 1, wherein said roller mounting means includes means adjustably positioning said roller to locate the point of tangential contact of its contoured surface and the line of thrust pressure against the periphery of the wheel circumferentially thereof in predetermined spaced relation from a plane parallel to the slide and intersecting the axial center of said wheel.

3. The combination defined in claim 1, in which said means for angularly adjusting the roller supporting means includes a bracket carried by the slide, together with means adjustably mounting the roller supporting means on said bracket for movement relative to the slide to locate the point of tangential contact of the contoured surface of the roller and the line of thrust pressure against the periphery of the wheel circumferentially thereof in predetermined spaced relation from a plane parallel to the slide and intersecting the axial center of said wheel.

4. The combination defined in claim 1, in which said means for angularly adjusting the roller supporting means comprises a saddle on said slide, a supporting cradle for the roller rockable in said saddle transversely of the slide, and means for releasably clamping said cradle in adjusted position in the saddle.

5. The combination defined in claim 1, in which said means for angularly adjusting the roller supporting means comprises a saddle on said slide, means for transversely adjusting said saddle on the slide, a supporting cradle for the roller rockable in said saddle transversely of the slide, and means for releasably clamping said cradle in adjusted position in the saddle. V

6. In wheel dressing mechanism for a grinding machine having a rotatable grinding wheel, a base adapted to be mounted on the machine in proximity to the grinding wheel, a slide movable on said base toward and from the periphery of the wheel, a wheel dressing tool mounted on said slide, a shaft, means in the base mounting said shaft for axial and rotative movement, a nut threaded on said shaft and means connecting said nut with the slide, restraining the nut against rotation while permitting relative movement between the slide and nut axially of the shaft, an energy storing device coacting with said nut and a part on the slide, means for rotating said shaft in the retracted position of the slide, to move the nut, slide and energy storing device as a unit axially thereof and initially position the dressing tool in predetermined spaced relation to the wheel, and additional means operatively connected to said shaft mounting means for axially moving said shaft to advance the slide and energize said storing device, after pressure contact between the tool and wheel, to continue the advancing movement of the slide independently of said shaft and cause the tool to penetrate the peripheral face of the wheel to a depth corresponding to said initial adjustment of the tool.

7. The combination defined in claim 6, wherein said mounting means comprises a bearing supporting said shaft and slidably keyed in the base, and said additional means comprises manually operable means on the base connected with said bearing to impart unitary axial movement to said bearing and shaft.

8. The combination defined in claim 6, wherein said means for mounting the shaft comprises a rack on which the shaft is rotatably mounted, and said additional means comprises a manually operable pinion coacting with said rack.

9. The combination defined in claim 6, wherein said means for mounting the shaft comprises a rack on which the shaft is rotatably mounted, and said additional means comprises a manually operable pinion coacting with said rack, together with means mounted in the base and coacting with the rack to yieldably retain the shaft and slide in retracted position.

10. In combination with a grinding machine having a motor driven abrasive wheel, a contouring roller mounted in opposed relation to the periphery of said wheel, means for applying a pressure force to said roller to cause its contoured surface to penetrate the peripheral face of the abrasive wheel to a predetermined depth, an operating motor for said roller, a circuit for said motor, and means in said circuit automatically operable when said predetermined depth of penetration of the abrasive Wheel is reached to open the circuit and de-energize said motor.

11. The combination defined in claim 10, wherein said force applying means includes manually operable means for moving said roller into and'out of contact with said wheel, and switch means in the roller motor circuit actuated to closed position by a part of said manually operable means to maintain said motor in energized condition during pressure engagement of the contouring roller with the abrasivewheel.

12. The combination defined in claim 10, together with an operating motor for the abrasive wheel and a circuit energizing said motor to rotate the wheel in grinding direction, a reversing circuit for said wheel motor, means for closing the circuit for the roller motor upon pressure engagement of the roller with the abrasive wheel, and means interconnected with said last named means for simultaneously closing the reversing circuit of the abrasive wheel motor to drive said wheel in a reverse direction during the pressure contouring operation of said roller.

13. In combination with a grinding machine having an abrasive wheel, an operating motor therefor, a contouring roller mounted in opposed relation to the periphery of said wheel, means for applying a pressure force to said roller to cause its contoured surface to penetrate the peripheral face of the abrasive wheel to a predetermined depth, an operating motor for said roller, energizing circuits for the respective motors, start and stop switches in the wheel motor circuit, additional switch means in said circuit controlled by the abrasive wheel and maintained in closed position during rotation of said wheel in grinding direction, means responsive to operation of said stop switch for closing a motor reversing circuit through said additional switch means, and apply braking torque to said wheel, means for closing the energizing circuit for the roller motor upon pressure engagement of said roller with the abrasive wheel, and means interconnected with said last-named means for simultaneously closing the reversing circuit of said abrasive wheel motor independently of said additional switch means, to drive said wheel in the reverse direction during the pressure contouring operation of said roller.

14. The combination defined in claim 13, together with means in the roller motor circuit automatically operable to open said circuit and deenergize the motor when the contouring roller has penetrated the face of the abrasive wheel to a predetermined depth.

15. The combination defined in claim 13, to-

gether with means in the reversing circuit for base adapted to be mounted on a machine frame in proximity to an abrasive grinding wheel, a slide movable on said base toward and away from the periphery of said wheel, a wheel dressing roller rotatably mounted on said slide, and actuating means for said slide comprising an energy storing device, fixed means on said slide supporting one end of said device, a member slidably mounted on said slide supporting the opposite end of said device, a manually operable element having a, threaded connection with said member, a sleeve slidably mounted in said base rotatably supporting said element, means preventing relative axial movement between the said sleeve and said element, and means in said base operatively connected with said sleeve and l to the slide to render said energy storing device effective to continue advancing movement of the slide and urge said roller into the peripheral face of the grinding wheel.

CECIL W. HOPKINS. ROY I. EYLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 675,936 Dawson June 11, 1901 722,810 Carter Mar. 17, 1903 1,373,833 Roberts Apr. 5, 1921 1,513,758 Hanson Nov. 4, 1924 1,608,367 Buckingham Nov. 23, 1926 1,639,253 Norton Aug. 23, 1927 1,896,533 Vuilleumier Feb. 7, 1933 2,135,202 Scrivener Nov. 1, 1938 2,220,768 Indge Nov. 5, 1940 2,237,974 Wainwright Apr. 8, 1941 2,286,046 Wickman June 9, 1942 FOREIGN PATENTS Number Country Date 26,499 Great Britain Dec. 2, 1902 514,221 Germany Dec. 9, 1930 518,019 Great Britain Feb. 15, 1940 519,081 Great Britain Mar. 15, 1940 526,075 Great Britain Sept. 10, 1940 542,918 Great Britain Feb. 2, 1942 

